Many types of equipment either come with Eye Bolts or are fitted with Eye Bolts for lifting purposes.
There are some considerations when you use such Eye Bolts:

1) Eye Bolts are marked with their thread size, NOT with their rated capacities. ONLY Swivel Hoist Rings are marked with their rated capacities.   5) Use only eye bolts which are designed for LIFTING. Do not use “no name” products. You cannot determine the steel grade by “feel” or “look”.
2) If you assume that a standard eye bolt has the same angularity strength loss factor as your sling, YOU ARE WRONG.
A sling used at a horizontal angle of (for example) 45° retains 71% of its VERTICAL capacity.
A standard eye bolt used with that same 45° horizontal angle retains just a mere 30% of its VERTICAL capacity. This is important if you shackle an eye bolt into a sling and assume that if the VERTICAL sling capacity matches the VERTICAL eye bolt capacity you have a safe sling system. Nothing is farther from the truth!
  6) Use Shoulder (Machinery) Eye Bolts for angled lifts.
  7) It is BEST to use Swivel Hoist Rings for EVERY angled lift. They adjust to any sling angle by rotating around the bolt and the hoisting eye pivots 180°.
  8) For a further discussion on how to safely use eye bolts please refer to our CROSBY® catalogue, or ask your local UNIROPE representative for advice.
3) NEVER, and that means NEVER, rig a sling through eye bolts. You severely increase the stress on the eye bolt and the bolt can break.   With Regular
(non Shoulder) eye bolts, use a spreader bar to keep the lift angle at 90° to the horizontal.
4) Although eye bolts can be used down to a 30° horizontal angle, we DO NOT RECOMMEND this practice. The strength loss of an eye bolt approaches 75% of vertical rated capacity, and any even slight decrease in horizontal lifting angle may break the bolt.  
  Never reeve slings through eye bolts. This alters the load and the angle of loading.
We recommend that eye bolts only be used at a horizontal angle greater than 45°. Sling strength at 45° is 71% of vertical sling capacity.
Eye bolt strength at 45° horizontal angle drops down to 30% of vertical lifting capacity.
Use swivel hoist rings for rigging. They self adjust to any load angle and are clearly marked with their capacity and recommended
torque values.
  At 45° lifting angle eye bolts have just 30% of their rated VERTICAL capacity. A sling (any type) used at the same 45° angle retains 71% of its vertical capacity.